--I just think, a rogue who has +6 in every trained skill, always succeding on hard tasks, without rolling at all sucks.
--It is just, that I don´t see a reason, why a rogue should be better at religion, if he choses to be a priest, than a cleric etc.
Having tested the Rogue's auto +3 for ability mod and the Take 10 rule... I would also agree that it's been rather lame. Always having a floor of 16 every time the Rogue made a skill check removed most of the drama.
My own personal preference is that rather than the auto +3 and the Take 10... the Rogue just gets to make every skill check with Advantage as standard. His chance to succeed is now much greater than everyone else... but there's
still the slight chance of failure. It's much more in keeping with the whole theory of 'bounded accuracy', where no one should be numerically priced out of a challenge (either with success or failure) based upon what the other characters in the party can do.
So thus even the low-Wis Rogue making a check to find a trap still gets to roll twice and probably succeed more often than the high-Wis Cleric. And what's better about that, is that it also emulates the situation that *if* the PCs are trying to make a check in a bad situation (because of combat, weather, or any of those sorts of things)... while the rest of the party all make the check with Disadvantage... the Rogue gets to just make the check normally (as his Advantage and the Disadvantage cancel each other out).
That being said... in reference to your second point though, I disagree. Because you're still looking at the class/skill connection through the eyes of previous editions, where it was your class that told you how good you were supposed to be at all these skills. 'A Cleric is a religious class, and thus should have the best Religion check'.
But in DDN that's no longer the case. It's not the class that tells you what your focus and study has been over these past years as you've learned stuff... it's your Background. Cleric now no longer implies 100% that he is the end-all-be-all religious character. All being a Cleric means is that he has the power to cast Divine spells. He has the spark of the divine in him... but that doesn't mean he's a would-be Cardinal. With the advent of the Background system... now classes
outside of the divine spellcasters can have just as much knowledge and training in religion (and in many cases, even more) as the Cleric does.
After all... a Cleric Commoner might just be a young urchin boy who's been 'touched by a god' to do great things in his name and given these odd magical blessings with which to do them. Whereas a Rogue Priest might be an archivist of a Church who's never been blessed by his god to use magic, but instead has devoted his life to working and running within the Church hierarchy. So it makes easy sense why the Rogue would have the better chance to succeed at Religious Lore checks than the Cleric.
Now granted... the disconnect could certainly come when a player at some table somewhere selects Rogue for his class and Priest for his background but then never actually plays the character very priestly or actually used his background for character development. And the player of the Cleric would then rightly ask "why is his character better at Religious Lore than mine is?"... but that's a probably more of not playing the character you've built, as opposed to some flaw within the game system itself.